FIG. 1 is a front elevational view of a conventional inserter system 100. As seen from FIG. 1, the inserter system 100 includes a control panel 102, and several sheet feeder towers 104 arranged along a sheet transport path 106. Each sheet feeder tower 104 may, for example, include two or more sheet feeders that hold and contain feed trays for paper sheets and inserts. The sheets are fed from the sheet feeders along the sheet transport path to a pre-fold accumulator 108. In the case of at least some mail pieces to be assembled by the inserter system 100, two or more sheets are accumulated to form a collation, which is then fed downstream to a folder 110.
The inserter system 100 also includes an envelope feeder 112. Envelopes are fed from the envelope feeder 112 to an insertion station 114, at which each folded collation is inserted into a respective one of the envelopes. Sealing and metering of the resulting mail pieces may be performed downstream from the inserter system 100, in a mailing machine which is not shown.
FIGS. 2A and 2B schematically illustrate operation of a divert gate 202 positioned upstream from the pre-fold accumulator 108. Also schematically shown in FIGS. 2A and 2B is a sheet transport mechanism 203 that transports paper sheets in a downstream direction (indicated by arrow 204 in FIG. 2A) to the pre-fold accumulator 108. The pre-fold accumulator 108 includes one or more drive belts (discussed further below, not separately shown in FIGS. 2A and 2B) which drive the sheets toward a pre-fold accumulator gate (not separately shown). Until the collation of sheets is complete, the pre-fold accumulator gate blocks the sheets so that they are held in the pre-fold accumulator 108.
On occasion, a collation is too large to be folded by the folder 110. In such a case, it is necessary to outsort the collation from the fold/insertion transport path. This is accomplished in cooperation with the divert gate 202, in a manner schematically illustrated in FIG. 2B. As shown in FIG. 2B, the oversize collation (not shown) is fed in a reverse or upstream direction (indicated by arrow 206) by the drive belt(s) (not separately shown), such that the oversize collation contacts the divert gate (in its open position shown in FIG. 2B) and is diverted downwardly (as indicated by arrow 208) out of the normal feed path.
According to a previously proposed arrangement, the divert gate 202 is biased by a spring (not shown) towards the open position shown in FIG. 2B. A stop (which is not shown) limits the upward movement of the divert gate 202 to define the open position. During normal feeding of a sheet from the sheet transport mechanism 203 toward the pre-fold accumulator 108, the sheet pushes downwardly against the divert gate 202 against the force of the spring to push the divert gate 202 to its closed position (shown in FIG. 2A) to allow the sheet to be fed to the pre-fold accumulator 108. Once the sheet clears the divert gate 202, the spring pushes the divert gate 202 back to the open position shown in FIG. 2B to allow for outsorting/diverting of the collation, if necessary.
There are potential problems with the spring-driven divert gate arrangement, as described above. For example, the spring must provide enough force to reliably return the divert gate 202 to its open position, yet not so much force that the divert gate 202 fails to close when a sheet is fed in the downstream direction over the divert gate 202 from the upstream transport. In practice, it has been difficult to arrive at a suitable amount of spring force. In some cases, the spring selected has provided too much force, and as a result, in the case of a relatively light sheet, the divert gate may fail to close upon downstream feeding of the sheet against the divert gate, resulting in the sheet crashing upwardly against the system frame (not shown) and failing to reach the pre-fold accumulator. However, if the spring force were to be reduced, the response time in opening of the divert gate may not be rapid enough for desired operation of the inserter system.